History’s Most Influential Psychologists

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Although it was some 2,500 years ago when the great Athenian philosophers Plato and Aristotle became the first westerns to ponder the mysteries of life from a psychological perspective, it wasn’t until the 19th century, not long after the immortalized French medical doctor Pierre Cabanis began speaking about the science of man, when the field of psychology was recognized as a distinguished area of scientific study. While the discipline’s history has been brief in comparison to many of the world’s other esteemed academic subjects, this by no means is to say that the field’s evolution has progressed slowly. In fact, ever since the late 1800s, each passing decade has unfailingly given rise to a number of influential psychologists who’ve systematically improved our understanding of the brain and human behavior.

Thanks to the work of these legendary figures, who’ve conceptualized a variety of enduringly significant psychological theories, in addition to a valuable base of psychological approaches, the field has not only become one of the world’s fastest-growing but also one of the most important. Here, we’ve done our best to illuminate the most notable contributions and wisdom-filled words of ten historically significant psychological figures, coming from the schools of Psychoanalysis, Behaviorism, Humanistic, and Cognitive, while simultaneously outlining the evolutionary path of the field.

Before we begin this exploratory journey, it should be pointed out that because this article looks at the discipline’s greatest minds from a historical lens, we’ve regrettably had to omit nearly all of this generation’s most influential psychologists. Doing so, however, certainly wasn’t done with the intention of diminishing the importance of the contributions made by individuals such as Daniel Kahneman, Martin Seligman, Howard Gardner, and Barbara Fredrickson. With that being said, let’s now turn our attention toward two of psychology’s earliest influencers.

Psychology’s Earliest Influencers:

To accurately explore the historical roots of psychology, we must begin our journey by traveling back in time to Germany during the 1860s and 70s. It was here where the iconic psychologist Wilhelm Wundt, the man most consider to be the father of the field, taught the first higher education psychology course at the University of Heidelberg in 1864, published the first book pertaining to the discipline, Principles of Physiological Psychology, in 1874 and opened the first experimental psychological lab at the University of Leipzig in 1879.

It wasn’t long after Wundt, who aimed to dissect psychological matters down to their smallest parts by employing the perspective of structuralism, helped establish the field as an area of scientific study, a number of other eminent figures, such as Gestalt Psychology’s founding father Max Wertheimer, took on prominent roles influencing the field. Yet still, there are perhaps no two figures from the discipline’s earliest years who influenced the study of the brain and human behavior like William James and Sigmund Freud.

William James:

Where as Wilhelm Wundt is rightfully thought of as the father of the broader psychological field, the late great William James (January 11, 1842 – August 26, 1910) is more specifically remembered as the founding father of American psychology. Of course, this is because it wasn’t long after the aforementioned Wundt taught the first university psychology course on European soil and wrote the discipline’s first important book when James followed a path remarkably similar to his colleague from across the pond. It was in 1875, to be exact, when James taught the first American psychology course at Harvard University and in 1890 when he’d publish what would become one of the field’s earliest classics, The Principles of Psychology.

In addition to this important pioneering work, the man some believe did more for the discipline than any other 19th century figure systematically laid the field’s groundwork by researching and theorizing about topics such as emotions, habits, consciousness and free will. Moreover, the functionalist approach James relied upon to study the brain and human behavior, which aims to discover the reasons why humans developed their current psychological characteristics, eventually morphed into the distinguished branch of Evolutionary Psychology. For his contributions to the field, the American Psychology Association (APA) ranked James 14th on their list of the Top 100 Eminent Psychologists of the 20th Century. The father of American psychology flashed his psychological brilliance, which was well advanced for the times, when he told us:

The world we see that seems so insane is the result of a belief system that is not working. To perceive the world differently, we must be willing to change our belief system, let the past slip away, expand our sense of now, and dissolve the fear in our minds.”

Sigmund Freud:

There is perhaps not a single individual who’s impact on the field of psychology, and the world at large, can match that of the iconic Austrian psychologist Sigmund Freud (May 6, 1856 – September 23, 1939). While many of his most notable theories, on topics such as the ego, sexual libido and the relationship between a mother and child for example, have been sharply criticized and thoroughly debunked by the influential psychologists who came after him, there’s little doubt that his work remains important and his historical influence will forever hold weight. Moreover, although some of history’s most important psychological movements originated out of opposition to Freud’s work, the polarizing psychologist mentored a number of other historically notable psychologists including Alfred Adler, Carl Jung and his daughter Anna Freud.

In stark contrast to some of his most famous yet faulted theories, a number of Freud’s other notable contributions forever transformed the direction of the field and our approach to treating mental health disorders. It was around the turn of the 20th century, which is referred to as ‘Freud’s Century’ by some, when the iconic psychologist developed his psychodynamic therapeutic approach that’s built upon the premise of patients talking openly about their problems with their therapists. Additionally, the overarching concept of his unconscious mind theory, which tells us various memories, thoughts and feelings remain out of one’s awareness yet influence their behavior, has stood the test of time as being true. Of this unknown part of the mind, he told us:

There is a powerful force within us, an unilluminated part of the mind – separate from the conscious mind that is constantly at work molding our thoughts, feelings, and actions.”

Eminent Behavioral Psychologists:

Not long after the psychological approach of psychoanalysis emerged as the field’s first dominant perspective, a second major school of thought arose out of opposition to Sigmund Freud’s theories which placed great emphasis on understanding the introspective nature of human experience. It was in the early decades of the 1900s when the work of a number of historically influential figures such as Edward Thorndike and John B. Watson shaped the behavioral perspective that aims to limit psychologists’ focus to only behavior.

It was largely because psychologists at the time were struggling to objectively understand the subjective nature of the mind that Behavioral Psychology rose to prominence throughout the first half of the 20th century. While Thorndike’s law of effect, which he publicly presented in 1898, marked one of the first major contribution to the behaviorist movement, and Watson, who carried out the famed Little Albert experiment, formally established the behavioral school in 1913, the work of two other behavioral giants may have had the greatest impact on the broader field.

Ivan Pavlov:

Throughout the 150 year history of psychological exploration, few experiments have stood the test of time as being truly groundbreaking and even fewer that’ve used animals as the subject of the research. Undoubtedly, one such experiment that did just that was carried out by the great Russian psychologist Ivan Pavlov (September 14, 1849 – February 27, 1936). It was during the later years of the 19th century when Pavlov accidentally discovered classical conditioning, the term used to describe the process of unintentionally developing habitual biological responses to previously neutral stimuli in the environment, while he was studying the physiology of digestion in his pet dogs.

The famed discovery occurred when Pavlov began noticing his canines secreting saliva whenever they saw an assistant researcher whom they’d associated with being fed. From this observation, the great psychologist and his team shifted the focus of their research to determine if previously unknown environmental cues (a bell) could become associated with future events (being feed) in a way that creates involuntary condition reactions (salivation). It was largely due to Pavlov’s research, which made its way to the western world in the early 1900s, that the behavioral branch of psychology was established. For his discovery, Pavlov, who was one of the first researchers to advocate for the humane treatment of experimental animals, was awarded with the Nobel Prize for Physiology or Medicine in 1904. The famed psychologist advised his peers to refuse becoming satisfied with the surface level findings of their research:

Do not become archivists of facts. Try to penetrate to the secret of their occurrence, persistently search for the laws which govern them.”

B.F. Skinner:

While there were a number of influential psychologists who helped develop and popularize Behavioral Psychology, the man who unquestionably became the face of the movement was B.F. Skinner (March 20, 1904 – August 18, 1990). Similar to Ivan Pavlov, who made an important discovery about the development of habitual behavior that stood the test of time, so too did Skinner with his theory of operant conditioning. Where as the iconic Russian psychologist’s discovery related to involuntary biological responses and neutral environmental stimuli, however, the immortalized American’s findings revealed a distinctive type of conditioning that develops when individuals learn to associate positive and negative outcomes with their actions. Over time, these associations, which encourage and discourage particular behaviors, are strengthened through what Skinner called reinforcement.

To study and verify his theory of operant conditioning, the famed Harvard psychologist developed an experimental apparatus known as the Skinner Box which allowed him to test and monitor animals as they interact with their environment. Thanks to his work, numerous professional and educational organizations still rely upon Skinner’s theory to motivate their employees and students. In addition to operant conditioning, Skinner also developed a number of other behavioral theories and published 21 books including his 1938 psychology classic The Behavior of Organisms and his 1948 novel Walden Two which was based upon his scientific research. Although many of his behavioral hypotheses have fallen out of favor since he passed away, Skinner’s contributions to the field, honorary degrees and awards speak for themselves. In fact, his career was so impactful that some believe him to be the most influential psychologist of the 20th century. The eminent behaviorist, who didn’t believe men can ultimately make decisions with free will, told us:

Behavior is shaped and maintained by its consequences.”

Iconic Humanistic Psychologists:

Up until around the 1930s, the two psychological approaches of psychoanalysis and behaviorism largely shaped the field’s understanding of the brain and human behavior. That was until Humanistic Psychology emerge as psychology’s third major school of thought in response to the limitations of the work done by Freud, Skinner and others. In stark contrast to the pessimistic perspective of psychoanalysis and the restrictive view of behaviorism, the humanistic approach was built upon the notion that all individuals are inherently good and have the ability to move themselves towards happiness and fulfillment.

While the two iconic humanistic psychologists that we’ll examine below, Carl Rogers and Abraham Maslow, are widely thought of as the movement’s most important figures, a number of other influential psychologists contributed to the holistic approach which focuses on ideas such as human potential, subjective experience, creatively becoming and finding meaning. For example, the work of Otto Rank, Viktor Frankl, Rollo May, Fritz Perls and Laura Perls were all of great importance to the field. Thank to this distinctively optimistic branch of psychology, other prominent subfields, such as Transpersonal Psychology and Positive Psychology, and therapeutic strategies, such as Gestalt Therapy and Existential Psychotherapy, have come about.

Carl Rogers:

When examining the psychological contributions made by history’s most influential psychologists, it becomes clear to see that few individuals have been able to impact the field like Carl Rogers (January 8, 1902 – February 4, 1987). Not only is late great American psychologist considering to be one of the founding father of Humanistic Psychology, and therefore a grandfather figure of Positive Psychology, he also revolutionized the field with his Person-Centered Therapeutic Approach. While the great minds before him had confidence in diagnosing their patients and prescribing solutions to fix their problems, with almost a sense of arrogant superiority, Rogers’ approach, which was outlined in his highly acclaimed 1951 book Client-Centered Therapy, was based upon the belief that the psychologist and client are equals. Therefore, instead of making assumptions based upon the limited amount of time they spent with their patients, Rogers advocated for listening, understanding and guiding them towards the discovery of their own answers.

In addition to establishing Humanistic Psychology and developing Client-Centered Therapy, which remains widely utilized in therapeutic, educational and industrial settings, Carl Rogers offered valuable insights on human development, personality, incongruence and acceptance. Throughout his career, the immortalized psychologist wrote 19 books in total, including On Becoming a Person in 1961 and A Way of Being in 1980, served as the President of the American Psychological Association (APA) and received numerous awards. Yet still, what’s perhaps Rogers’ most impressive accomplishment was that he was nominated for the 1987 Noble Peace Prize, which was awarded to none other than Mother Teresa, for working to resolve a conflict between South Africa and Ireland. Of how his view of his role as a psychologist changed during his career, Rogers told us:

In my early professional years I was asking the question: How can I treat, or cure, or change this person? Now I would phrase the question in this way: How can I provide a relationship which this person may use for his own personal growth?”

Abraham Maslow:

Throughout modern history there have been a plethora of iconic figures, coming from a wide variety of backgrounds, who’ve rose above distressing life circumstances to inspire others and bring positive change to the world. As was the case with Abraham Maslow (April 1, 1908 – June 8, 1970), it was the disheartening years of his youth, and later the devastating effects of the second world war, that gave rise to a modest yet brilliant man. Although he didn’t have a supportive environment at home, dealt with anti-Semitic racism throughout the younger years of his life and even was diagnosed as being ‘mentally unstable’ by a therapist, the now immortalized humanistic psychologist was able to transform the field by shining light on humans’ positive traits. Unquestionably, Maslow’s most notable contribution came in the form of his Hierarchy Of Needs theory which systematically outlines the psychological needs an individual must appease in order to achieve the ultimate human desire to realize one’s fullest potential, or what Maslow called self-actualization.

Beyond his most celebrated insights on psychological needs and self-actualization, Abraham Maslow will forever be considered as one of the founding fathers of Humanistic Psychology, alongside Carl Rogers, because his theories on peak experiences, wholesome mental states and personal growth served as foundational elements of the approach. Furthermore, the great American psychologist’s books Hierarchy Of Needs: Theory of Human Motivation and Toward a Psychology of Being, published in 1943 and 1963 respectively, are considered as two of psychology’s true classics. For his contributions to the field, Maslow was named as the Humanist of the Year in 1967 by the American Humanist Association (AHA) and still to this day has an award bearing his name that’s annually bestowed by the American Psychological Association (APA). On why he ultimately decided to focus on the positive attributes of humans, Maslow told us:

The science of psychology has been far more successful on the negative than on the positive side; it has revealed to us much about man’s shortcomings, his illnesses, his sins, but little about his potentialities, his virtues, his achievable aspirations, or his psychological height. It is as if psychology had voluntarily restricted itself to only half its rightful jurisdiction, and that the darker, meaner half.”

Prominent Figures of the Cognitive Revolution:

While the psychological approaches of psychoanalysis, behaviorism and humanism dominated the field until the later decades of the 20th century, the 40 years between 1930 and 1970 served as a vastly important evolutionary period for the discipline’s future. Not only was it during these four decades when the branches of Developmental Psychology and Social Psychology were formally established, but it was also during this time period when a variety of influential psychologists commenced the movement known as the cognitive revolution.

By coming to discover a wide range of flaws with the theories and methods found within the psychoanalytic and behavioral schools of thoughts, prominent psychologists such as Lev Vygotsky and Leon Festinger, who were both highly critical of their predecessors, were able to stoke the field’s interest in studying the functional role mental processes play in the human experience. Additionally, the work of others such as George A. Miller, who’s 1956 article The Magical Number Seven, Plus or Minus Two remains one of the field’s most cited, and Noam Chomsky, who adamantly rejected B.F. Skinner’s idea of radical behaviorism, undoubtedly helped transform the discipline. Yet still, while these immortalized figures certainly propelled the field forward, it’s hard to overlook the groundbreaking work of Jean Piaget and Jerome Bruner.

Jean Piaget:

Although it’s said that the cognitive revolution started in the early 1950s, it’s nearly impossible to separate the work that developmental psychologist Jean Piaget (August 9, 1896 – September 16, 1980) conducted in the 1930s from the greater psychological movement. In fact, because the celebrated Swiss psychologist was the first to systematically study the process of mental development in children, it’s safe to consider him as one of the revolution’s earliest pioneers. Certainly, his most notable contribution to the field comes in the form of Piaget’s theory of cognitive development which tells us there are four distinctive developmental stages (the sensorimotor stage, the preoperational stage, the concrete operational stage and the formal operational stage) that children progress through as they actively expand their intellectual dexterity.

By coming to realize that kids think differently then adults, and gradually enhance their intelligence through a dynamic process of learning, the self described genetic epistemologist was not only able to peek his peers interest in the cognitive dynamics of human existence but also single handedly transform education, parenting and childcare in western societies. In addition to his most important theory, which has undergone slight modifications, Piaget’s insights on cognitive schemas, information processing and equilibration assuredly influenced the prominent figures of the cognitive revolution. For his contributions, the man who ranks as one of the most influential psychologists of all time has been bestowed with numerous honorary degrees and awards such as the prestigious Erasmus Prize in 1972 and the International Balzan Prize in 1979. When discussing what he believed should be the aim of education, Piaget told us:

The principle goal of education in the schools should be creating men and women who are capable of doing new things, not simply repeating what other generations have done.”

Jerome Bruner:

In comparison to the late great Jerome Bruner (October 1, 1915 – June 5, 2016), there is perhaps not a single individual who did more to usher in psychology’s cognitive era. It was after becoming discouraged with the field’s dominant approach of behaviorism in the 1940s when the iconic psychologist first began studying the human mind and his contributions over the following two decades would prove to be invaluable to the development of the cognitive approach. Not only did Bruner’s groundbreaking research on the active processes of perception and sensation open up a new avenue for psychological study, but his 1956 book A Study of Thinking and his role founding the Harvard’s Center for Cognitive Studies in 1960, alongside colleague George A. Miller, were undoubtedly significant to the cognitive revolution and the formalization of Cognitive Psychology.

In addition to his pioneering work during what was perhaps the most important movement in the field’s history, the legendary psychologist, who’s interest in studying the mind may have stemmed from the fact that he was born blind and spent the first two years of his life living in a visual world he constructed without sight, contributed to a number of other psychological branches including Developmental, Educational, and Legal. Moreover, his research on language and learning was similarly important for psychology’s broader evolution. For the numerous contributions he made throughout what would become a 70-year career, Jerome Bruner will forever be remembered as one of the discipline’s most influential cognitive figures. While most of his peers fell in line with the field’s most celebrated thinkers and standard operating proceeders, Bruner ushered in a new age by thinking outside the box. He told us:

The shrewd guess, the fertile hypothesis, the courageous leap to a tentative conclusion – these are the most valuable coins of the thinker at work. But in most schools guessing is heavily penalized and is associated somehow with laziness.”

Distinguished Cognitive Psychologists:

With the pioneering work of Jean Piaget, Jerome Bruner and others like Allen Newel as a foundational base, psychology’s fourth major school of thought emerged around 1970. It was in 1967, to be exact, when the man who’s commonly thought of as the father of the cognitive perspective, American psychologist Ulric Neisser, published his groundbreaking book Cognitive Psychology and moved the new approach to the forefront of the field. While the world’s most influential psychologists remained interested in studying observable behavior after Neisser’s landmark work, Cognitive Psychology would gradually become the discipline’s most prominent branch.

Within the later decades of the 20th century, the cognitive approach has vastly increased our knowledge of the brain and human behavior as a plethora of distinguished psychologists, who study our brain’s hardwiring as if it were a computer, have made historic discoveries related to a variety of mental processes such as thinking, perception, memory and judgment. Still to this day, the likes of David M. Buss, Elizabeth Loftus and Steven Pinker continue to deepen our understanding of the mind as some of the field’s most celebrated figures. Yet still, throughout the branch’s brief history, there have been few cognitive psychologists who’ve influenced the perspective more so than Albert Bandura and Albert Ellis.

Albert Bandura:

While there is no denying the fact that the distinguished American psychologist Albert Bandura (born December 4, 1925) played a major role in stoking the cognitive revolution and subsequently shifting the field’s dominate perspective from behavioral to cognitive, his numerous contributions have spanned across a 60 plus year career and much of his most important work has occurred after Cognitive Psychology was formalized as one of discipline’s major branches. Bandura first became a household name in 1961 after conducting his now legendary Bobo doll experiment that showed how children learn behaviors by observing and imitating older adults. From this research, the influential social cognitive psychologist developed the social learning theory which he later expanded, to give a more comprehensive view of the relationship between cognitions and socially learned behaviors, and renamed as the social cognitive theory.

Some years later, in the 1970s, the now 92-year-old Bandura, who’s considered by many to be the greatest living psychologist, switched his focus and began studying the role beliefs play on individuals’ capacity to manage situations and act in ways that produce the most desirable outcomes. From this work, Bandura developed his theory of self-efficacy which tells us that one’s own beliefs about their abilities largely determine the likelihood of their success. For the contributions he’s made throughout his illustrious career, Albert Bandura has been bestowed with numerous honorary degrees and awards including the United States’ most prestigious scientific award, the National Medal of Science. Of the governing role cognitions have over our actions, he told us:

What people think, believe, and feel affects how they behave. The natural and extrinsic effects of their actions, in turn, partly determine their thought patterns and affective reactions.”

Albert Ellis:

Just as the aforementioned Albert Bandura can be considered as one of the truly distinguished figures of the cognitive revolution, so too can the iconic American psychologist Albert Ellis (September 27, 1913 – July 24, 2007). Similarly, just as Bandura’s work impacted the field far beyond the initial phases of the field’s evolution towards Cognitive Psychology, so too has the work of the man Psychology Today proclaimed as having the greatest impact on modern psychotherapy. It was in the late 1940s when Ellis, who believed that each of us can cultivate happiness and fulfillment within ourselves, broke away from the conventional therapeutic approach of psychoanalysis and began developing a new method that blended cognitive, emotional and behavioral strategies. By the mid 1950s, the iconic psychologist had gone public with his new approach, Rational Emotive Behavior Therapy (REBT), and begun teaching it to other therapists.

Although his new therapeutic strategy, which he continued to tinker with until he passed away, was met with fierce resistance from the traditional psychotherapeutic establishment throughout the 1950s, Ellis wouldn’t be discouraged and as his approach gained evidence-based validity, he’d soon become one of the field’s most influential figures. In the following decade, the famed psychologist, who also played a prominent role in the American Sexual Revolution, began his next monumental project by working with the late great psychiatrist Aaron T. Beck. While the latter is generally considered the founding father of Cognitive Behavioral Therapy (CBT), which is one of the most effective therapeutic approaches today, the method’s foundation was largely built upon the former’s ideas. For the immense contributions he made to the field, Albert Ellis has been bestowed with numerous awards and remains considered one of history’s most influential psychologists. Of our ability to nurture a wholesome psychological state, Ellis told us:

You have considerable power to construct self-helping thoughts, feelings and actions as well as to construct self-defeating behaviors. You have the ability, if you use it, to choose healthy instead of unhealthy thinking, feeling and acting.”